Pressure Decay Leak Check Method and Apparatus

ABSTRACT

Refrigerant recovery unit is provided that includes steps to test for refrigerant leaks. The steps include providing a close loop with the hoses that connect to a refrigerant system, measuring the ambient temperature, calculating the vapor pressure with the ambient temperature, calculating the test pressure as a percentage of the vapor pressure, filling the unit with the refrigerant, and performing a pressure leak test.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to provisional U.S. patent applicationentitled “Pressure Decay Leak Check Method and Apparatus,” filed May 12,2011, having Ser. No. 61/487,075, now pending, the disclosure of whichis hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The disclosure generally relates to equipment for servicing vehicle airconditioning systems, and more particularly a method that checks forpressure decay leak in a refrigerant recovery unit used to service avehicle.

BACKGROUND OF THE INVENTION

Portable refrigerant recovery units or carts are used in connection withthe service and maintenance of refrigeration systems such as a vehicle'sair conditioning system. The refrigerant recovery unit connects to theair conditioning system of the vehicle to recover refrigerant out of thesystem, separate out oil and contaminants from the refrigerant in orderto recycle the refrigerant, and recharge the system with additionalrefrigerant.

New refrigerants such as 1234yf are flammable and thus having a leak cancause a fire in the refrigerant recovery units. The leak can affect theperformance and accuracy of the refrigerant recovery units, and cancause harmful refrigerant to be released into the atmosphere. Because1234yf refrigerant can be relatively expensive, having a method todetect the leaks will save money for the service center that owns therefrigerant recovery units and fixing any leak is also beneficial forthe environment.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, arefrigerant recovery unit is provided and includes a method to check fora pressure decay leak.

In one embodiment of the invention, a method of performing a pressureleak test on a refrigerant recovery unit is provided, which can comprisemeasuring an ambient temperature with a temperature sensor controlled bya controller of the refrigerant recovery unit, determining a saturatedvapor pressure with the measured ambient temperature using thecontroller, determining a test pressure as a percentage of thedetermined saturated vapor pressure using the controller, measuring afirst pressure in the refrigerant recovery unit with a pressure sensorcontrolled by the controller, and determining if the refrigerantrecovery unit has passed the pressure leak test with the controller.

In another embodiment of the invention, a method of performing apressure leak test on a refrigerant recovery unit is provided, which cancomprise measuring an ambient temperature with a temperature sensorcontrolled by a controller of the refrigerant recovery unit, determininga saturated vapor pressure with the measured ambient temperature usingthe controller, determining a test pressure as a percentage of thedetermined saturated vapor pressure, and determining if the refrigerantrecovery unit has passed the pressure leak test with the controller.

In yet another embodiment of the invention, a refrigerant recovery unithaving a pressure leak test is provided, which can comprise a recoverycircuit configured to recover a refrigerant from a refrigerant system, acharging circuit configured to charge the refrigerant into therefrigerant system, a recycling circuit configured to recyclerefrigerant recovered from the refrigerant system, a refrigerant storagetank in fluid communication with the recovery, charging and recyclingcircuits, and a controller that controls the recovery, charging andrecycling circuits, wherein the controller performs the following steps:measuring an ambient temperature with a temperature sensor, determininga saturated vapor pressure with the measured ambient temperature,determining a test pressure as a percentage of the determined saturatedvapor pressure, measuring a first pressure in the refrigerant recoveryunit with a first pressure sensor, determining if the measured firstpressure of the refrigerant recovery unit is above the determined testpressure, and determining if the refrigerant recovery unit has passedthe pressure leak test.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of embodiments inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the present invention. It is important,therefore, that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary front plan view of an example refrigerantrecovery unit shown with a portion of the front cover removed accordingto an embodiment of the invention.

FIG. 2 is a fragmentary rear plan view of the refrigerant recovery unitshown in FIG. 1 according to an embodiment of the invention.

FIG. 3 is an example of a flow diagram of the refrigerant recovery unitshown in FIGS. 1 and 2 according to an embodiment of the invention.

FIG. 4 is a front plan view of another example refrigerant recovery unitaccording to an embodiment of the invention.

FIG. 5 is another example of a flow diagram of the refrigerant recoveryunit shown in FIGS. 1, 2 and 4 according to an embodiment of theinvention.

FIGS. 6A and B illustrate a method to check for refrigerant leaks thatmay occur in the refrigerant recovery unit according to an embodiment ofthe invention.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawingfigures, in which like numerals refer to like parts throughout. Arefrigerant recovery unit is provided that includes the ability toself-check for refrigerant leaks in order to prevent continued ventingof a refrigerant into the atmosphere.

FIGS. 1 and 2 show an example of a portable refrigerant recovery unit 10(recovery unit) constructed according to principles of the invention,for recovering, recycling, and recharging refrigerant from a refrigerantsystem of a vehicle. Other refrigerant systems, such as ones in a houseor a building, are also within the embodiments of this invention.

The refrigerant recovery unit 10 is a machine having a cabinet 20supported by a pair of wheels 22, for portability. The refrigerantrecovery unit 10 includes a first container or main tank 12 for holdinga primary supply of refrigerant, such as 1234yf. The main tank 12 mayalso be referred to as an internal storage vessel (ISV). The main tank12 contains refrigerant that has been recovered from the airconditioning system. The refrigerant recovery unit 10 also includes asecond container or auxiliary tank 14 for holding a secondary supply ofrefrigerant. The secondary supply of refrigerant has a known chemicalcomposition, and is sometimes referred to as fresh refrigerant, virginrefrigerant or recharging refrigerant. The auxiliary tank 14 is arrangedto be in fluid communication with the main tank 12 so that freshrefrigerant can be transferred from the auxiliary tank 14 to the maintank 12, as needed.

An electronic controller 16 includes a microprocessor on a circuit board17. The electronic controller 16 controls, among other things, thetransfer of refrigerant from the auxiliary tank 14 to the main tank 12and between the main tank 12 and a refrigeration system 74 (FIG. 3). Thecontroller 16 also controls electromechanical solenoid valves, includingsolenoid valves 76, 78, 80, 84, 88, 96, 98, 100 (FIG. 3). However, eachsolenoid valve in the refrigerant recovery unit 10 may be connected andcontrolled by the controller 16. The controller 16 may include a memoryunit (not shown) to store software and data, and the microprocessor maybe coupled to the memory unit for executing the software stored in thememory unit. The electronic controller 16 receives data signals from avariety of devices and sensors, including pressure sensors 92, 95,temperature sensors 68 that measure the ambient temperature, controlswitches (on the control panel 32), and a weighing device 34.

The weighing device 34 shown in the example embodiment is a load cell,but the weighing device may also be any type of electronic scale or anyother type of weighing device configurable to transmit a weight datasignal to the controller 16. As shown in FIG. 2, the main tank 12 restson the weighing device 34. The weighing device 34 provides a weight datasignal to the controller 16 such that the weight of the tank comprisingits tare weight plus the weight of refrigerant therein is monitored bythe controller 16.

The control panel 32 includes an on/off switch 35 and a display 36 fordisplaying the operational status of the refrigerant recovery unit'soperation. The display 36 may also display instructions to a user of therefrigerant recovery unit 10. The display may be an LCD display or othersuitable electronic display that is coupled to the controller 16 by wayof a conventional input/output circuit. The control panel 32 furtherincludes a switch panel 38 having a conventional keyboard 40, and aplurality of push-button switches 42 for controlling the operation ofthe refrigerant recovery unit 10 through its various phases of operationand/or for selecting parameters for display. The keyboard 40 inconjunction with push-button switches 42 and display 36 allow the userto enter the desired operational parameters for the refrigerant recoveryunit 10 according to manufacturer specifications for the servicing of anair conditioning system in a particular vehicle.

The refrigerant recovery unit 10 includes a high pressure hose 24,typically color coded red, with a coupling 26 for coupling to the highpressure port of a vehicle refrigeration system and a low pressure hose28, typically color coded blue, having a coupling 30 for coupling to thelow pressure port. The couplings 26 and 30 can also be coupled back intothe refrigerant recovery unit at storage ports 71 so as to form a“closed loop.” In various embodiments, either the couplings 26, 30 canbe coupled together or can be coupled together through an intermediaryhose. That is coupling 26 can be coupled at one end of the intermediaryhose and coupling 30 can be coupled at the other end.

In some refrigerant systems, there may be only one port, for example,where the recovery or low pressure port is eliminated. In such systems,the refrigerant recovery unit may be configured with one hose, inaccordance with the principles of the invention.

The front panel of the cabinet 20 is shown broken away in FIG. 1 to showthe major elements of the refrigerant recovery unit 10. The hoses 24 and28 are coupled to pressure gauges 44 and 46, respectively, which aremounted on the front panel of refrigerant recovery unit 10, as seen inFIG. 1. In addition, electrical pressure transducers (not shown) may becoupled to the hoses 24 and 28, and to the controller 16 throughconventional input/output circuits to provide the controller 16 withpressure information during operation of the refrigerant recovery unit10. Gauges 44 and 46 provide the user with a conventional analog ordigital display of the pressure.

Mounted to the floor 54 of cabinet 20 is a fluid compressing means orcompressor 56 and a vacuum means or vacuum pump 58. Behind the front ofcabinet 20 on floor 54, is mounted the main tank 12 of refrigerant (FIG.2) for the supply of refrigerant to the refrigerant system beingserviced. Also, mounted adjacent the main tank 12 is the auxiliarysupply tank 14 which supplies additional refrigerant to the main tank12. Hoses and connectors together with control valves couple auxiliarysupply tank 14 to main tank 12.

Mounted to the inside of rear wall 60 of cabinet 20 is an oil separator62 and a compressor oil separator filter 64. A pressure transducer 92(FIG. 3) is coupled to the oil separator so that pressure in therefrigerant recovery unit 10 can be measured. In addition, a fresh oilcanister 70 is mounted within a side compartment of cabinet 20. Arecovery or waste oil container 72 is mounted on the lower part of thecabinet 20 to receive oil drained from the oil separator 62.

Having briefly described the major components of the refrigerantrecovery unit 10, a more detailed description of the structure andoperation of the example refrigerant recovery unit 10 follows inconnection with reference to FIG. 3.

With respect to a recovery process, one example of a refrigerantrecovery circuit is described below and shown in FIG. 3. To recoverrefrigerant, initially, hoses 24 and 28 (FIG. 1) are coupled to therefrigeration system 74 of a vehicle, and the recovery cycle isinitiated by the opening of high pressure and low pressure solenoids 76,78, respectively. This allows the refrigerant within the refrigerationsystem 74 to flow through a recovery valve 80 and a check valve 82. Therefrigerant flows from the check valve 82 into a system oil separator62, where it travels through a filter/dryer 64, to an input of acompressor 56. Refrigerant is drawn through the compressor 56 through anormal discharge solenoid 84 and through the compressor oil separator86, which circulates oil back to the compressor 56 through an oil returnvalve 88. The refrigerant recovery unit 10 includes a high pressureswitch 90 in communication with the controller 16, which is programmedto determine an upper pressure limit, for example, 435 psi, to shut downthe compressor 56 to protect the compressor 56 from excessive pressure,although this feature is optional. If a purging of the refrigerantrecovery unit 10 is desired, a high-side clear solenoid (not shown) mayoptionally be coupled to the output of the compressor 56 to release therecovered refrigerant transferred from compressor 56 directly into themain tank 12, instead of through a path through the normal dischargesolenoid 84.

The heated compressed refrigerant exits the oil separator 86 and thentravels through a loop of conduit or heat exchanger 91 for cooling orcondensing. As the heated refrigerant flows through the heat exchanger91, it gives off heat to the cold refrigerant in the system oilseparator 62, and assists in maintaining the temperature in the systemoil separator 62 within a working range. Coupled to the system oilseparator 62 is a switch or transducer 92, such as a low pressure switchor pressure transducer, for example, that senses pressure information,and provides an output signal to the microprocessor 16 through asuitable interface circuit programmed to detect when the refrigerantrecovery unit 10 has recovered the refrigerant down to 13 inches ofmercury, for example. The pressure transducer 92 can be used todetermine the pressure in the refrigerant recovery unit 10. Finally, therecovered refrigerant flows through a normal discharge check valve 94and into the main tank 12.

The evacuation cycle begins by the opening of high pressure and lowpressure solenoids 76 and 78 and valve 96, leading to the input of avacuum pump 58. Prior to opening valve 96, an air intake valve (notshown) is opened, allowing the vacuum pump 58 to start up exhaustingair. The vehicle system 74 is then evacuated by the closing of the airintake valve and the opening of valve 96, allowing the vacuum pump 58 toexhaust any trace gases remaining until the pressure is approximately 29inches of mercury, for example. When this occurs, as detected bypressure transducers optionally coupled to the high side and low side ofthe refrigeration system 74 and to the controller 16, the controller 16actuates valve 96 by turning it off and beginning the recharging cycle.

The recharging cycle begins by opening charge valve 98, 99 to allow theliquid refrigerant in tank 12, which is at a pressure of approximately70 psi or above, to flow through the high side of the refrigerationsystem 74. A pressure transducer 95 can be used to measure the pressurein the tank 12. The flow is through charge valve 98, 99 for a period oftime programmed to provide a full charge of refrigerant to the vehicle.

FIG. 4 is a front plan view of another example refrigerant recovery unit200 according to an embodiment of the invention. The refrigerantrecovery unit 200 can be the CoolTech 34788™ from Robinair™ based inOwatonna, Minn. (Service Solutions U.S. LLC). The refrigerant recoveryunit 200 includes a cabinet 202 to house components of the system (SeeFIG. 5). The cabinet 202 may be made of any material such asthermoplastic, steel and the like.

The cabinet 202 includes a control panel 204 that allows the user tooperate the refrigerant recovery unit 200. The control panel 204 may bepart of the cabinet as shown in FIG. 4 or separated. The control panel204 includes high and low gauges 206, 208, respectively. The gauges maybe analog or digital as desired by the user. The control panel 204 has adisplay 210 to provide information to the user, such as certainoperating status of the refrigerant recovery unit 200 or providemessages or menus to the user. Located near the display 210 are LEDs 212to indicate to the user the operational status of the refrigerantrecovery unit 200. A user interface 214 is also included on the controlpanel 204. The user interface 214 allows the user to interact andoperate the refrigerant recovery unit 200 and can include analphanumeric keypad and directional arrows.

The cabinet 202 further includes connections for hoses 224, 228 thatconnect the refrigerant recovery unit 200 to a refrigerant containingdevice, such as the vehicle's refrigerant system 300 (shown in FIG. 2).An ambient temperature sensor 230 may be located on the cabinet 202 tomeasure the ambient temperature around the refrigerant recovery unit200. Additionally, storage ports 232 may be used to connect hoses 224,228 back into the refrigerant recovery unit 200 to form a “close loop.”In order for the refrigerant recovery unit 200 to be mobile, wheels 220are provided at a bottom portion of the system.

FIG. 5 illustrates components of the refrigerant recovery unit 200 ofFIG. 4 according to another embodiment of the present invention. In oneembodiment, to recover refrigerant, service hoses 224 and 228 arecoupled to the refrigeration system 300 of the vehicle, via couplers 326(high side) and 330 (low side), respectively. The couplers are designedto be closed until they are coupled to the refrigerant system 300.

The recovery cycle is initiated by the opening of high pressure andlow-pressure solenoids 376, 378, respectively. This allows therefrigerant within the vehicle's refrigeration system 300 to flowthrough a recovery valve 380 and a check valve 382. The refrigerantflows from the check valve 382 into a system oil separator 362, where ittravels through a filter/dryer 364, to an input of a compressor 356.Refrigerant is drawn through the compressor 356 through a normaldischarge solenoid 384 and through a compressor oil separator 386, whichcirculates oil back to the compressor 356 through an oil return valve388. The refrigerant recovery unit 200 may include a high-pressureswitch 390 in communication with a controller 316, which is programmedto determine an upper pressure limit, for example, 435 psi, tooptionally shut down the compressor 356 to protect the compressor 356from excessive pressure. The controller 316 can also be, for example, amicroprocessor, a field programmable gate array (FPGA) orapplication-specific integrated circuit (ASIC). The controller 316 via awired or wireless connection (not shown) controls the various valves andother components (e.g. vacuum, compressor) of the refrigerant recoveryunit 200. In some embodiments of the present disclosure, any or all ofthe electronic solenoid or electrically activated valves, pressure andtemperature sensors may be connected and controlled by the controller316.

A high-side clear solenoid 423 may optionally be coupled to the outputof the compressor 356 to release the recovered refrigerant transferredfrom compressor 356 directly into a storage tank 312, instead of througha path through the normal discharge solenoid 384.

The heated compressed refrigerant exits the oil separator 386 and thentravels through a loop of conduit or heat exchanger 391 for cooling orcondensing. As the heated refrigerant flows through the heat exchanger391, the heated refrigerant gives off heat to the cold refrigerant inthe system oil separator 362, and assists in maintaining the temperaturein the system oil separator 362 within a working range. Coupled to thesystem oil separator 362 is a switch or transducer 392, such as a lowpressure switch or pressure transducer, for example, that sensespressure information, and provides an output signal to the controller316 through a suitable interface circuit programmed to detect when thepressure of the recovered refrigerant is down to 13 inches of mercury,for example. An oil separator drain valve 393 drains the recovered oilinto a container 357. Finally, the recovered refrigerant flows through anormal discharge check valve 394 and into the storage tank 312.

The evacuation cycle begins by the opening of high pressure andlow-pressure solenoids 376 and 378 and valve 396, leading to the inputof a vacuum pump 358. Prior to opening valve 396, an air intake valve(not shown) is opened, allowing the vacuum pump 358 to start exhaustingair. The vehicle's refrigerant system 300 is then evacuated by theclosing of the air intake valve and opening the valve 396, allowing thevacuum pump 358 to exhaust any trace gases remaining until the pressureis approximately 29 inches of mercury, for example. When this occurs, asdetected by pressure transducers 331 and 332, optionally, coupled to thehigh side 326 and low side 330, respectively, of the vehicle'srefrigeration system 300 and to the controller 316, the controller 316turns off valve 396 and this begins the recharging cycle.

The recharging cycle begins by opening charge valve 398 to allow therefrigerant in storage tank 312, which is at a pressure of approximately70 psi or above, to flow through the high side of the vehicle'srefrigeration system 300. The flow is through charge valve 398 for aperiod of time programmed to provide a full charge of refrigerant to thevehicle. Optionally, charge valve 399 may be opened to charge the lowside. The charge valve 399 may be opened alone or in conjunction withcharge valve 398 to charge the vehicle's refrigerant system 300. Thestorage tank 312 may be disposed on a scale (not shown but similar toscale 434) that measures the weight of the refrigerant in the storagetank.

Other components shown in FIG. 5 include an oil inject circuit having anoil inject valve 302 and an oil inject hose or line 311. The oil injecthose 311 is one example of a fluid transportation means for transmittingoil for the refrigerant recovery unit 200. The oil inject hose 311 maybe one length of hose or multiple lengths of hose or tubing or any othersuitable means for transporting fluid. The oil inject hose 311 connectson one end to an oil inject bottle 314 and on the other end couples tothe refrigerant circuit in the refrigerant recovery unit 200. Disposedalong the length of the oil inject hose 311 are the oil inject valve 302and an oil check valve 304. The oil inject path follows from the oilinject bottle 314, through the oil inject solenoid 302, to the junctionwith the high side charge line 326, and to the vehicle's refrigerantsystem 200.

FIG. 5 also illustrates a vacuum pump oil drain circuitry 350 thatincludes a vacuum pump oil drain valve 352 that is located along avacuum pump oil drain conduit 354 connecting a vacuum pump oil drainoutlet 359 to the container 357 for containing the drained vacuum pumpoil. The vacuum pump oil drain valve 352 may be an electronicallyactivated solenoid valve controlled by controller 316. The activationmay be a wireless or wired connection. In other embodiments the valve352 may be a manually activated valve and manually actuated by a user.The conduit 354 may be a flexible hose or any other suitable conduit forprovided fluid communication between the outlet 359 and the container357.

FIG. 5 also illustrates an air purging apparatus 408. The air purgingapparatus 408 allows the refrigerant recovery unit 200 to be purged ofnon-condensable, such as air. Air purged from the refrigerant recoveryunit 200 may exit the storage tank 312, through an orifice 412, througha purging valve 414 and through an air diffuser 416. In someembodiments, the orifice may be 0.028 of an inch. Although the orificemay be larger or smaller, as desired than 0.028 in. A pressuretransducer 410 may measure the pressure contained within the storagetank 312 and purge apparatus 408. The pressure transducer 410 may sendthe pressure information to the controller 316. And when the pressure istoo high, as calculated by the controller, purging is required for thestorage tank 312. The valve 414 may be selectively actuated to permit ornot permit the purging apparatus 408 to be open to the ambientconditions. A temperature sensor 417 may be coupled to the main tank tomeasure the refrigerant temperature therein. The placement of thetemperature sensor 417 may be anywhere on the tank or alternatively, thetemperature sensor may be placed within a refrigerant line 422. Themeasured temperature and pressure may be used to calculate the idealvapor pressure for the type of refrigerant used in the refrigerantrecovery unit. The ideal vapor pressure can be used to determine whenthe non-condensable gases need to be purged and how much purging will bedone in order to get the refrigerant recovery unit 200 to functionproperly.

High side clearing valves 418 may be used to clear out part of thehigh-pressure side of the unit 200. The high side clearing valves 418may include valve 423 and check valve 420. Valve 423 may be a solenoidvalve. When it is desired to clear part of the high side, valve 423 isopened. Operation of the compressor 356 will force refrigerant out ofthe high pressure side through valves 423 and 420 and into the storagetank 312. During this procedure the normal discharge valve 384 may beclosed.

A deep recovery valve 424 is provided to assist in the deep recovery ofrefrigerant. When the refrigerant from the refrigerant system 300 has,for the most part, entered into the refrigerant recovery unit 200, theremaining refrigerant may be extracted from the refrigerant system 300by opening the deep recovery valve 424 and turning on the vacuum pump358.

In another embodiment, in order to charge the refrigerant system 300,the power charge valve 426 may be opened and a tank fill structure 432may be used. Alternatively or in addition to, the tank fill structure432 may also be used to fill the storage tank 312. In order to obtainrefrigerant from a refrigerant source, the refrigerant recovery unit 200may include the tank fill structure 432, and valves 428 and 430. Thetank fill structure 432 may be configured to attach to a refrigerantsource. The valve 430 may be a solenoid valve and the valve 428 may be acheck valve. In other embodiments, valve 430 may be a manually operatedvalve.

When it is desired to allow refrigerant from a refrigerant source toenter the refrigerant recovery unit 200, the tank fill structure 432 isattached to the refrigerant source and the tank fill valve 430 isopened. The check valve 428 prevents refrigerant from the refrigerantrecovery unit 200 from flowing out of the refrigerant recovery unit 200through the tank fill structure 432. When the tank fill structure 432 isnot connected to a refrigerant source, the tank fill valve 430 is keptclosed. The tank fill valve 430 may be connected to and controlled bythe controller 316.

The tank fill structure 432 may be configured to be seated on the scale434 configured to weigh the tank fill structure 432 in order todetermine an amount of refrigerant stored in the tank fill structure432. The scale 434 may be operatively coupled to the controller 316 andprovide a measurement of a weight of the tank fill structure 432 to thecontroller 316. The controller 316 may cause a display of the weight ofthe tank fill structure 432 on the display 210.

As the refrigerant recovery unit 10, 200 operate under pressure,refrigerant leaks will occur over time. These leaks need to be fixed sothat refrigerants are not vented into the atmosphere. Further, newrefrigerants such as 1234yf are flammable and thus, can be a firehazard. FIG. 6A and 6B illustrate a method 500 to check for refrigerantleaks that may occur in the refrigerant recovery unit 10, 200. Thismethod may be conducted manually, via software implementing the methodor a combination of both. These steps may be implemented on either orboth of refrigerant recovery unit 10, 200, but will be described inrelation to refrigerant recovery unit 200.

At step 502, the method begins. At step 504, an instruction appears onthe display and instructs the user to connect the hoses 224, 228 tostorage ports 232. By connecting or coupling the hoses 224, 228 to thestorage ports 232, a “closed loop” is formed in the refrigerant recoveryunit 200. Additionally, this allows the hoses and their associatedcouplers to all be pressure leak tested. Alternatively, the couplersthat attach the refrigerant recovery unit 200 to the hoses 224, 228 maybe shut off for the pressure leak test.

At step 506, the ambient temperature can be measured using thetemperature sensor 230 and the measured temperature can be relayed tothe controller 316. The temperature sensor 230 can be located at anypart of the refrigerant recovery unit 200 such as on the side of thecabinet.

At step 508, determine whether the ambient temperature is less thanabout 10° C. The refrigerant recovery unit 10 operates at about 10° C.so the pressure leak test would not be performed below this temperaturebecause mixing warm refrigerant (from the storage tank that has recentlyrecovered refrigerant) with refrigerant in the refrigerant recovery unit200 that was not operating at the normal temperature can skew theresults of the test or provide false positives. In other embodiments,the refrigerant recovery unit 200 may operate at a lower or highertemperature such as 6-9° C. or 11-13° C. depending on the manufacturer.

If yes at step 508, then proceed to step 510, where the user is informedvia the display that the temperature is too low to run the leak test.Then the method ends at step 512. If no at step 508, then proceed tostep 514.

At step 514, the saturated vapor pressure is calculated using theambient temperature measure by the temperature sensor 230. In oneembodiment, the following formulas are used:

y=pressure in psig

x=temperature in ° F.

For R-134a:

y=(4.7157887*10⁻⁸)*x ⁴+(1.2348358*10⁻⁵)*x ³+(5.3215*10⁻³)*x²+(4.740976*10⁻¹)*x+6.6407031

For R-1234yf:

y=(4.6512538*10⁻⁸)*x ⁴+(98.3574939*10⁻⁶)*x ³+(5.0550861*10⁻³)*x²+(4.9971197*10⁻¹)* x ²+9.0615092

At step 516, once the saturated vapor pressure is calculated in step514, then measure the pressure in the refrigerant tank 312, via thepressure transducer 410, and determine if the pressure in therefrigerant tank 312 is greater than about one bar above the calculatedsaturated vapor pressure. In other embodiments, the pressure can beabout between 2-4 bars. If yes, then proceed to step 518 where the useris informed on the display that the pressure in the refrigerant tank istoo high to perform the pressure leak test and the method ends at step520. If at step S216, the answer is no, then proceed to step 522 wherethe user is informed, via the display, that the pressure leak test is inprogress.

At step 524, calculate the test pressure as a percentage of thecalculated saturated vapor pressure for the measured ambienttemperature. The percentage can be from about 45-98%, from about 60-98%,from about 75-95%, from about 80-90%, from about 90-98% and any rangeabove or below. The closer the test pressure is to the saturated vaporpressure, the better. At step 526, measure the pressure in therefrigerant recovery unit through the pressure transducer 392 and relaythe measured pressure to controller 316. The appropriate valves in therefrigerant recovery unit can be opened so that the pressure of the unitcan be properly measured. At step 528, determine if the measuredpressure in the refrigerant recovery unit is greater than the calculatedtest pressure. If no, then proceed to step 532. If yes, then proceed tostep 530 where the refrigerant recovery unit 200 operates in therecovery function to reduce the refrigerant in the unit and thereby,reduce the pressure in the unit. This can be done automatically by therefrigerant recovery unit 200 or manually by user being prompted on thedisplay. Then proceed to step 532.

At step 532, fill refrigerant recovery unit with refrigerant to raisethe pressure in the unit to the calculated test pressure. This can bedone automatically by the refrigerant recovery unit 200 or manually byuser being prompted on the display. As refrigerant is circulated in therefrigerant recovery unit 200, the pressure is increased. At step 534,calculate the leak test time based on calculated test pressure. In oneembodiment, time can be 222985/sqrt(pressure). If the unit is cool thena longer leak time can be used and if the unit is already warm, then ashorter leak test time can be used. Similarly, if the pressure is low,then a longer leak test time can be used. Conversely, if the pressure ishigh, then a shorter leak test time can be used. However, any amount oftime can be used as long as it is enough to detect leaks includingsmaller leaks. Additionally, the leak test can be simply run for a fixedamount of time without being calculated. For example, for 3 minutes, 5minutes, 7 minutes, 10 minutes, or other times.

At step 536, display, via the display, the leak test in progress with acountdown timer. The timer may be 5 minutes. At step 538, determine ifat least 45 seconds has passed. Other time that can be utilized at thisstep include a range of 15-60 seconds, 30-45 seconds or any other timeperiod that will stabilize the unit for proper testing parameters. Ifno, then proceed back to step 536 to complete the 45 seconds. If yes,then proceed to step 540, where the current pressure of the refrigerantrecovery unit is measured and stored to the memory. At step 542, thedisplay can display that the leak test is in progress and the countdowntimer is the amount determined in step 534.

At step 544 determine if pressure in the refrigerant recovery unit hasdecreased by 0.20 bar from the saved measured pressure of step 540.Other amounts can be used including 0.10-0.80 bar, 0.15-0.70 bar orother pressure amounts. If no, then at step 548 determine if leak testtime is at 0? If not, then return to step 542. If yes, then at step 550,informed the user, via the display, that the pressure leak test passed.That is, the refrigerant recovery unit passed the pressure leak test.Then end at step 560. Returning to step 544, if yes, then proceed tostep 546 and inform the user, via the display, that the pressure leaktest failed. Then end at step 560.

By running the pressure leak test described herein, the refrigerantrecovery unit can be checked for leaks. This allows the refrigerantrecover unit to operate within the relevant industry standards.

The many features and advantages of the invention are apparent from thedetailed specification, and thus, it is intended by the appended claimsto cover all such features and advantages of the invention which fallwithin the true spirit and scope of the invention. Further, sincenumerous modifications and variations will readily occur to thoseskilled in the art, it is not desired to limit the invention to theexact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

1. A method of performing a pressure leak test on a refrigerant recovery unit, comprising the steps of: measuring an ambient temperature with a temperature sensor controlled by a controller of the refrigerant recovery unit; determining a saturated vapor pressure with the measured ambient temperature using the controller; determining a test pressure as a percentage of the determined saturated vapor pressure using the controller; measuring a first pressure in the refrigerant recovery unit with a pressure sensor controlled by the controller; and determining if the refrigerant recovery unit has passed the pressure leak test with the controller.
 2. The method of claim 1 further comprising the steps of: determining if the measured first pressure of the refrigerant recovery unit is above the determined test pressure using the controller; determining a pressure leak test time based on the determined test pressure; and running the pressure leak test based on the determined pressure leak test time.
 3. The method of claim 2 further comprising the steps of: performing a recovery function if the measured first pressure of the refrigerant recovery unit is above the determined test pressure; and cycling refrigerant in the refrigerant recovery unit until the refrigerant recovery unit reaches the determined test pressure.
 4. The method of claim 1 further comprising the steps of: determining if the measured ambient temperature is below 10° C.; and alerting a user that the ambient temperature is too low to run the pressure leak test when the measured ambient temperature is below 10° C.
 5. The method of claim 1 further comprising the steps of: determining if a measured tank pressure is above the determined saturated vapor pressure; and alerting a user that the measured tank pressure is too high to run the pressure leak test when the measured tank is above the calculated saturated pressure.
 6. The method of claim 2 further comprising the steps of: allowing the refrigerant recovery unit to stabilize; measuring a second pressure of the refrigerant recovering unit with the pressure sensor; and saving the second pressure of the refrigerant recovery unit into a memory, wherein the refrigerant recovery unit passes the pressure leak test if a third measured pressure of the refrigerant recovery unit does not decrease beyond a predetermined amount from the saved the second measured pressure of the refrigerant recovery unit.
 7. The method of claim 6, wherein the predetermined amount is about 0.20 bar.
 8. The method of claim 2 further comprising the steps of: allowing the refrigerant recovery unit to stabilize; measuring a second pressure of the refrigerant recovering unit with the pressure sensor; saving the measured second pressure of the refrigerant recovery unit into a memory, wherein the refrigerant recovery unit fails the pressure leak test if a third measured pressure of the refrigerant recovery unit decreases beyond a predetermined amount from the saved second measured pressure of the refrigerant recovery unit.
 9. The method of claim 8, wherein the predetermined amount is about 0.20 bar.
 10. A method of performing a pressure leak test on a refrigerant recovery unit, comprising the steps of: measuring an ambient temperature with a temperature sensor controlled by a controller of the refrigerant recovery unit; determining a saturated vapor pressure with the measured ambient temperature using the controller; determining a test pressure as a percentage of the determined saturated vapor pressure; and determining if the refrigerant recovery unit has passed the pressure leak test with the controller.
 11. The method of claim 10 further comprising the steps of: determining a pressure leak test time based on the determined test pressure; and running the pressure leak test based on the determined pressure leak test time.
 12. The method of claim 11 further comprising the steps of: measuring a first pressure in the refrigerant recovery unit with a pressure sensor controlled by the controller; determining if the measured first pressure of the refrigerant recovery unit is above the determined test pressure using the controller; and reducing the measured first pressure of the refrigerant recovery unit if the measured first pressure is above the determined test pressure.
 13. The method of claim 10 further comprising the step of: cycling refrigerant in the refrigerant recovery unit until the refrigerant recovery unit reaches the determined test pressure.
 14. The method of claim 10 further comprising the steps of: determining if the measured ambient temperature is below 10° C.; and alerting a user that the ambient temperature is too low to run the pressure leak test when the measured ambient temperature is below 10° C.
 15. The method of claim 10 further comprising the steps of: determining if a measured tank pressure is above the determined saturated pressure; and alerting a user that the measured tank pressure is too high to run the pressure leak test when the measured tank pressure is above the determined saturated vapor pressure.
 16. The method of claim 11 further comprising the steps of: allowing the refrigerant recovery unit to stabilize; measuring a second pressure of the refrigerant recovering unit with the pressure sensor; and saving the second pressure of the refrigerant recovery unit into a memory, wherein the refrigerant recovery unit passes the pressure leak test if a third measured pressure of the refrigerant recovery unit pressure does not decrease beyond a predetermined amount from the saved second measured pressure of the refrigerant recovery unit.
 17. The method of claim 16, wherein the predetermined amount is about 0.20 bar.
 18. The method of claim 11 further comprising the steps of: allowing the refrigerant recovery unit to stabilize; measuring a second pressure of the refrigerant recovering unit with the pressure sensor; saving the second pressure of the refrigerant recovery unit into a memory, wherein the refrigerant recovery unit fails the pressure leak test if a third measured pressure of the refrigerant recovery unit pressure decreases beyond a predetermined amount from the saved second measured pressure of the refrigerant recovery unit.
 19. The method of claim 18, wherein the predetermined amount is about 0.20 bar.
 20. A refrigerant recovery unit having a pressure leak test, comprising: a recovery circuit configured to recover a refrigerant from a refrigerant system; a charging circuit configured to charge the refrigerant into the refrigerant system; a recycling circuit configured to recycle refrigerant recovered from the refrigerant system; a refrigerant storage tank in fluid communication with the recovery, charging and recycling circuits; and a controller that controls the recovery, charging and recycling circuits, wherein the controller performs the following steps: measuring an ambient temperature with a temperature sensor; determining a saturated vapor pressure with the measured ambient temperature; determining a test pressure as a percentage of the determined saturated vapor pressure; measuring a first pressure in the refrigerant recovery unit with a first pressure sensor; determining if the measured first pressure of the refrigerant recovery unit is above the determined test pressure; and determining if the refrigerant recovery unit has passed the pressure leak test.
 21. The refrigerant recovery unit of claim 20, wherein the controller further perform the following steps: determining a pressure leak test time based on the determined test pressure; and running the pressure leak test based on the determined pressure leak test time.
 22. The refrigerant recovery unit of claim 20, wherein the refrigerant storage tank is coupled to a second pressure sensor, wherein the second pressure sensor communicates with the controller.
 23. The refrigerant recovery unit of claim 20 further comprising of hoses configured to couple to hose couplers to form a closed loop with the refrigerant recovery unit. 